Both benzoquinones and naphthoquinones have been found to perturb protein handling and degradation in a variety of cellular systems. Protein handling and degradation is not restricted to the proteasome and also involves protein chaperones, the unfolded protein response (UPR)/endoplasmic reticulum (ER) stress response, formation of aggresomes and lysosomal autophagy. Quinones have been found to affect each of these systems and altered protein handling is emerging as a potentially key mechanism of quinone induced toxicity. Our studies will focus on model 1,4-benzo- and naphtho-quinones as well as the dopamine derived 1,2-quinone, aminochrome which have all been shown to induce changes in protein handling. In aim 1, we will characterize changes in all major protein handling systems induced by model benzo- and naphtho- quinones and by aminochrome. These experiments will characterize altered mechanisms of protein handling as a result of treatment of cells with reactive quinones and the relevance of such changes for toxicity in cellular systems. In aim 2, we will define the respective roles of arylation and quinone-induced oxidative stress in inhibited protein handling using quinones capable only of either redox cycling or of both redox cycling and arylation . We will also examine quinone induced changes in protein handling in cells stably transfected with the one electron reductases cytochrome P450 reductase or cytochrome b5 reductase which cause increased quinone one electron redox cycling and increased reactive oxygen generation. The major mammalian quinone reductases NQO1 and NQO2 are highly polymorphic with a high prevalence of variant alleles resulting in marked phenotypic changes. A lack or variation in activity of these enzymes may therefore represent susceptibility factors for quinone induced toxicity. In aim 3, we will examine the role of NQO1 and NQO2 in modulating quinone induced protein handling changes and toxicity. These experiments will be performed in isogenic pancreatic, breast and neural cellular systems specifically designed to explore the roles of NQO1 and NQO2 in the same genetic background Overall, these experiments will characterize novel mechanisms of quinone-induced toxicity at the level of protein handling, define the inter-relationships and the respective roles of protein handling changes in toxicity and define the role of NQO1 and NQO2 as susceptibility factors for these changes. The studies will have broad mechanistic applicability to a variety of organ systems.